42 Volt Automotive Systems 1

[harrisj]

I assumed that the so-called 42V systems proposed for the future were based on 36V battery technology. 42 is the voltage when charging.

A colleague has suggested that the 42V is the battery potential, giving about 49V when charging. This is to keep the maximum system voltage below the 'magic' 50Vdc safety threshold.

Which is correct?

John

 

[gcaudill]

42v - Nominal operating voltage
48v - Maximum operating voltage
58v - Maximum safe touch voltage

These are the values that have been proposed and seem to be generally accepted. Battery configurations are proposed at 36v.

Check out

http://www.sae.org/42volt

 

[johnnyw]

I understand that the "42 volt" system is well in progress, but I'm curious if anyone ever considered a 48 volt nominal battery system with the center point of the battery grounded to chassis. Essentially two 24 volt batteries in series with the center position grounded which would be very similar to household 240/120 vac distribution. For many loads either plus or minus 24 volts could be applied, and for the larger loads 48 volts could be applied. This would seem to limit the higher, more dangerous voltages to only a few locations where the positive and negative 24 volt leads are brought together for the large loads. With some effort, it might be feasible to have some "degraded" capability by switching leads around if part of the system fails. Would the use of 48 volts allow any commonality of parts from other industries (i.e., telecom)? How is the 60 volt safety level addressed for electric or hybrid vehicles where voltages are way in excess of 60 volts? Anyone have any other thoughts on this concept (i.e., charging technique, etc.)?

 

[brett12]

Automotive electronics is now based around stinging the consumer for the maximum amount of money possible, you can forget any "commonality of parts", if the manufacturers had their way you would only be able to put their own branded petrol/diesel in their cars. The introduction of digital electronics to cars has enabled them to make almost all parts of the system "coded" requiring dealer only or very expensive computer based equipment/software to make them work once fitted.
An example of this is the many cars are now employing the "central processing" type fuse box which incorporates computer control and relays/fuses in one unit. As a result of this, when the indicator relay fails (previosly an inexpensive flasher unit) you must now replace the entire unit at a cost of over £200 plus whatever the dealer wants to charge for coding the new unit to your car.
It's an embarresment to tell customers how much money they have to part with for such a simple fault.
The introduction of new higher voltage electrical systems is a great opportunity to squeeze yet more money out of consumers for something they really never asked for and dont need.It wont make cars more efficient either. the whole reason for upping the electrical output is to power more pointless gadgets in the passenger compartment, at the expense of fuel efficiency.
Sorry if this is a rant, but the car industry is all about profit, not engineering advantages of new systems.

 

[Ratty]

In answer to the question of whether those developing hybrid / electrical cars have thought about safety, the answer is yes, at least in part, they have.

I am aware of at least one example of a sensor being developed for the charging system of an electric car. Because an electric car is obviously silent and still when stationary, but not necessaryily inoperable, there is a possibility that pets left in the vehicle (including dogs and kids etc), may inadvertently drive off whilst the car is being charged. In comparison, a petrol engined car, quiet as they are these days, is still easily identifiable as running when you walk away from it after leaving your keys in it. Maybe common practice isn't to leave your kids in the car overnight whilst you charge it, but the possibility was highlighted and addressed.

As you would expect, the designs for the charging sockets and connectors eliminated any possibility of the customer accidently touching the contacts and coming into contact with the currents. I'm unsure of how the possibility of a damaged wire being touched by a customer was being made safe though?

Totally agree with the comments about the automotive industry asking embarrasing prices for simple jobs. To have brake disks and pads changed on my Peugeot 306 at the dealer was £350 plus a few years ago now - you can do it yourself in 15 minutes for £50. Market forces I'm afraid, if people are daft enough to pay and keep coming back, then that's business.